Comonomer content and distribution (CCD), also often called the short chain branching distribution (SCBD) is one of the key parameters controlling olefin-based polymer properties. A precise and accurate CCD analysis is critical for new product development. Current techniques use crystallization based (CEF, for example, see Monrabal and Mayo et al., Macromolecular Symposia, 2012; and TREF) or interaction based techniques (high temperature thermal gradient interaction chromatography, HT-TGIC, or a short abbreviation as TGIC (for example, see Cong and deGroot et al., Macromolecules, 2011, 44, 3062) to measure CCD. However, these techniques have the following shortcomings: limited resolution, one plate separation, and coelution/cocrystallization.
The most challenging issue in CEF, and all the other crystallization based separation techniques, is the co-crystallization (for example, see Alghyamah and Soares, Macromolecular Chemistry and Physics, 2014, 215, 465; & Macromolecular Chemistry and Physics, 2015, 216, 38), which leads to an error in SCBD results. On the other hand, the accuracy of HT-TGIC of olefin-based polymers is reduced because of poor resolution and coelution issues. These challenges make accurate SCBD modeling very difficult to achieve. Thus, there is a need for new chromatography techniques that improve resolution, and thus the accuracy, of a CCD (or SCBD) analysis. This need has been met by the following invention.